The present invention relates to a connector for a narrow pitch and also to an electrostatic actuator, a piezoelectric actuator, a micro machine, a liquid crystal panel, an ink jet head using these electrostatic actuator and piezoelectric actuator, an ink jet printer mounted with these ink jet heads, and an electronic appliance, each of which includes the connector for a narrow pitch.
In the recent years, electronic appliances have been configured acceleratedly more compact and lighter in weight. Along with this compact configuration of the electronic appliances, there have been stronger demands for parts to be used for the electronic appliances which are configured more compact and manufactured at lower costs. A micro working technology referred to as micro machining has been developed to cope with these demands and micro machines which are compact and have advanced functions have been manufactured. As an example of the micro machines, there is a printer head (hereinafter referred to as a printer engine) which has a built-in piezoelectric element and ejects ink by oscillating the built-in piezoelectric element.
An LCD cell of a liquid crystal panel is another example of part for which compact configuration is demanded.
To connect such a compact part to an external substrate, there as been used, for example, a method which interposes a connector composed of a flexible substrate, a method which uses wire bonding or a method which solders a wire cable.
FIG. 28 is an enlarged view showing main parts of a connection object and a connector composed of a flexible substrate. On a surface of a connection object 1 such as a printer engine an LCD cell of a liquid crystal panel, a plurality of wires 2 connected to an element are arranged and terminal electrodes 3 are formed at an end as shown in FIG. 28.
Used as a connector 4 which connects the connection object 1 to an external substrate is a flexible substrate which is made of a material of polyimide. Terminal electrodes 5 which can be overlapped with the terminal electrodes 3 formed at the end of connection object 1 are formed at an end of the substrate and terminal electrodes 6 which have a width greater than that of the terminal electrodes 5 are formed at a wider pitch at an end on a side opposite to the side at which the terminal electrodes 5 are formed. Wires 6A are arranged to connect the terminal electrodes 5 to the terminal electrodes 6, and the width and the pitch are changed in the course of the wires 6A.
FIG. 29 is a diagram descriptive of procedures for connecting the connection object 1 to the connector 4 and FIG. 30 is a sectional view taken along a Cxe2x80x94C line in FIG. 29.
In a case where the above described connection object 1 is to be connected to the connector 4 as shown in FIGS. 29 and 30, the connection object 1 is first placed on a bonding stage 7 so that the terminal electrodes 3 are set upside. Then, the terminal electrodes 5 arranged on the connector 4 are positioned to the terminal electrodes 3 and these terminals are overlapped with each other. An adhesive containing electrically conductive particles is applied between the terminal electrodes 3 and the terminal electrodes 5 so that the electrodes are electrically conductive by way of the electrically conductive particles.
A bonding tool 8 which can be raised and lowered is disposed over the overlapped electrodes, that is, over the terminal electrodes 5 of the connector 4. A heater 9 is built in the bonding tool 8 so that a tip of the bonding tool 8 can be heated by operating the heater 9.
At a bonding step, the electrodes are connected by lowering the bonding tool 8 and pressing the connector 4 with the bonding tool 8 so as to bring the electrically conductive particles into close contact with the electrodes and shorten a drying time of the adhesive by heating.
However, it is conventionally necessary to arrange connecting terminals on a micro machine or the like at a pitch which permits connection to a flexible substrate or the like since the flexible substrate is used for connecting the micro machine or the like to an external substrate. The pitch which permits connection to the flexible substrate is usually on the order of 100 xcexcM. The inventor has made various examinations and confirmed that a limit of a wiring pitch lies in the vicinity of 60 xcexcm for conventional connectors made of polyimide.
Accordingly, a terminal portion must be configured large only for enabling connection to the flexible substrate though actuators can be configured compact by the micro machining technology. As a result, there is posed a problem that the large terminal portion reduces a number of micro machines which can be cut out from a single silicon wafer.
Since manufacturing of the micro machines requires not only precise working typically represented by anisotropic etching of a silicon wafer but also expensive materials and expensive machines in particular, there has been desired to configure connecting terminals so as to occupy an area as small as possible, thereby manufacturing a large number of micro machines from a single silicon wafer with a high efficiency.
Furthermore, there is another problem that a trouble such as enhancement of a resistance value between terminals, improper joining or short circuit between adjacent terminals may be caused due to a difference between an coefficient of thermal expansion of a material (mainly silicon) of the connection object 1 and that of a material (mainly polyimide) of the connector 4.
This point will be described below in detail.
When the bonding tool 8 is brought near for connecting the connection object 1 to the connector 4, the connection object 1 and the connector 4 start swelling under an influence due to the heater 9 built in the bonding tool 8.
Since polyimide has a coefficient of thermal expansion which is larger than that of silicon at this time, the connector 4 swells larger than the connection object 1, thereby deviating the terminal electrodes 5 from the terminal electrodes 3 as shown in FIG. 31. Since the connection object 1 such as the printer engine or the LCD cell of liquid crystal panel is configured finer year by year and a pitch 10 between the electrode terminals 3 is narrowed to cope with the finer connection object (refer to FIG. 30), the trouble such as the enhancement of a resistance value between the terminals, improper joining or short circuit between adjacent terminals may be caused even when positions of the terminal electrodes are slightly deviated.
When the terminal electrodes are arranged at a narrower pitch and are thinner, a space reserved between adjacent terminal electrodes are smaller, thereby producing a fear that short circuit may be caused between the adjacent terminal electrodes.
The present invention relates to a narrow pitch connector which is capable of coping with fine pitches between electrodes, an electrostatic actuator, a piezoelectric actuator, a micro machine and a liquid crystal panel which include the narrow pitch connector, an ink jet head which uses the electrostatic actuator or the piezoelectric actuator, and an ink jet printer and an electronic appliance on which the ink jet heads are mounted.
(1) A narrow pitch connector in a mode of the present invention is a connector which comprises a plurality of first terminal electrodes and second terminal electrodes which are formed on a substrate, and wires which electrically connect the first terminal electrodes with the second terminal electrodes: the above described wires having a function of making conversion from a pitch of the first terminal electrodes to a pitch of the second terminal electrodes, wherein grooves are formed between the first terminal electrodes respectively.
By forming the grooves between the first terminal electrodes, the present invention makes it possible to prevent the terminal electrodes from being deformed by heat and pressure or shorted by outflow of an alloy or a metal at a step of an alloy bonding or a metal bonding even if the electrodes have a narrow pitch. Furthermore, the present invention makes it possible to lengthen a creeping distance between the adjacent terminal electrodes, thereby suppressing an influence due to noise.
(2) A narrow pitch connector in another mode of the present invention is the connector described in (1) above, wherein an insulating film is formed in the grooves.
By forming the insulating film in the grooves, the present invention makes it possible to prevent the first terminal electrodes from being electrically conductive to the substrate without fail.
(3) A narrow pitch connector in another mode of the present invention is the connector described in (2) above, wherein metal wires are formed on the insulating film formed in the grooves.
By arranging the metal wires on the bottom of the grooves, the present invention makes it possible to enhance a bonding strength between a connection object and the connector bonded with an adhesive. By enhancing the bonding strength, a connection with high humidity resistance can be realized.
(4) A narrow pitch connector in another mode of the present invention is the connector described in (3) above, wherein the metal wires are connected to the substrate, and a ground wiring portion or a power supply wiring portion.
Accordingly, a crystalline substrate can be set at a potential equal to that of the ground wiring portion or the power supply wiring portion, thereby stabilizing the potential of the crystalline substrate.
Furthermore, the narrow pitch connector is capable of preventing an erroneous operation of an element caused by line noise in a fine wiring portion and reducing radiation noise owing to an electrostatic shielding function.
(5) A narrow pitch connector in another mode of the present invention is the connector described in any one of (1) through (4) above, wherein the first terminal electrodes are electrodes to be electrically connected to external terminal electrodes formed on a connection object and the grooves are formed to reserve an adhesive for connecting the first terminal electrodes with the external terminal electrodes.
Accordingly, an excessive amount of the adhesive is accommodated into the grooves when joints are brought into close contact with the terminal electrodes and the electrically conductive particles contained in the adhesive are not caught at a location other than the terminal electrodes, so that outbreak of a short circuit between the adjacent terminal electrodes can be prevented.
(6) A narrow pitch connector in another mode of the present invention is the connector described in (5) above, wherein a depth of the grooves is set not shallower than three times a particle diameter of electrically conductive particles contained in the adhesive.
Accordingly, the narrow pitch connector is capable of accommodating the electrically conductive particles with a margin and enhancing a safety factor for prevention of short circuits. Furthermore, the connector is capable of enlarging a contact area and enhancing bonding strength since it allows the adhesive containing the electrically conductive particles to be reserved in the grooves.
(7) A narrow pitch connector in another mode of the present invention is the connector described in any one of (1) through (6) above, wherein the grooves are set longer than an overlapped portion of the terminal electrodes.
When the grooves have such a length, a portion enclosed by the connection object and the narrow pitch connector does not form a closed space at a bonding step, thereby hardly involves air, so that an adverse influence caused by air bubbles is not produced.
Furthermore, since excessive adhesive can be extruded without fail, thereby an internal pressure does not remain in the joints so that an adverse influence caused by the internal pressure is not produced.
(8) A narrow pitch connector in another mode of the present invention is the connector described in (5) above, wherein the connector is characteristic in that a coefficient of thermal expansion of the substrate is nearly equal to or smaller than that of the connection object.
Since the coefficient of thermal expansion of the substrate is nearly equal to that of the connection object as described above, a deviation of a relative position between the terminal electrodes to be connected each other is minimized at a step of bonding by pressing and heating.
When the coefficient of thermal expansion of the substrate is smaller than that of the connection object, a similar effect can be obtained by setting a main body of the connector at a temperature higher than the connection object and bonding them. (9) A narrow pitch connector in another mode of the present invention is the connector described in any one of (1) through (8) above, wherein the substrate is made of single-crystal silicon.
When the above described substrate is made of single-crystal silicon, the substrate is capable of enhancing a heat radiation effect and preventing a resistance value from increasing due to a temperature rise.
(10) A narrow pitch connector in another mode of the present invention is the connector described in (9) above, characterized in that a crystal face of the single-crystal silicon is a (100) face.
When the crystal face of the single-crystal silicon is the (100) face, a V-shaped groove can be formed at an angle of 54.74 degrees relative to the face by anisotropically etching the face. In addition, a depth of the V-shaped groove can be accurately controlled dependently on a width of a window (made, for example, of an SiO2 film) set on the (100) face.
(11) A narrow pitch connector in still another mode of the present invention is the connector described in (9) above, characterized in that the crystal face of the single-crystal silicon is a (110) face.
When the crystal face of the single-crystal silicon is the (110) face, a groove having a rectangular sectional shape can be formed by anisotropically etching the face. In this case, the groove can be formed at a predetermined depth independently of a width of the groove.
(12) A micro machine in another mode of the present invention comprises a moving mechanism portion and a first substrate on which a plurality of first terminal electrodes are formed, and is characterized in that the micro-machine further comprises a second substrate on which second terminal electrodes are formed to be electrically connected to the plurality of first terminal electrodes, a plurality of third terminal electrodes and wires for electrically connecting the second terminal electrodes with the third terminal electrodes are formed on the second substrate, the wires have a function of making conversion from a pitch of the second terminal electrodes to a pitch of the third terminal electrodes, and grooves are formed between the second terminal electrodes respectively.
(13) A piezoelectric actuator in another mode of the present invention comprises a piezoelectric element and a first substrate on which a plurality of first terminal electrodes are formed, and is characterized in that the actuator further comprises a second substrate on which second terminal electrodes are formed to be electrically connected to the first terminal electrodes, and a plurality of third terminal electrodes and wires for electrically connecting the second terminal electrodes with the third terminal electrodes are formed on the second substrate, the wires have a function of making conversion from a pitch of the second terminal electrodes to a pitch of the third terminal electrodes, and grooves are formed between the second terminal electrodes respectively.
(14) An electrostatic actuator in another mode of the present invention comprises an electrostatic oscillator and a first substrate on which a plurality of first terminal electrodes are formed, and is characterized in that the actuator further comprises a second substrate on which second terminal electrodes are formed to be electrically connected to the plurality of first terminal electrodes, a plurality of third terminal electrodes and wires for electrically connecting the second terminal electrodes with the third terminal electrodes are formed on the second substrate, the wires have a function of making conversion from a pitch of the second terminal electrodes to a pitch of the third terminal electrodes, and grooves are formed between the second terminal electrodes respectively.
(15) An ink jet head in another mode of the present invention comprises a piezoelectric element and a first substrate on which a plurality of first terminal electrodes are formed for ejecting an ink drop with the piezoelectric element, and is characterized in that the ink jet head further comprises a second substrate on which second terminal electrodes are formed to be electrically connected to the plurality of first terminal electrodes, a plurality of third terminal electrodes and wires for electrically connecting the second terminal electrodes with the third terminal electrodes are formed on the second substrate, the wires have a function of making conversion from a pitch of the second terminal electrodes to a pitch of the third terminal electrodes, and grooves are formed between the above described second terminal electrodes respectively.
(16) An ink jet head in another mode of the present invention comprises an electrostatic oscillator and a first substrate on which a plurality of first terminal electrodes are formed for ejecting an ink drop with the electrostatic oscillator, and is characterized in that the ink jet head further comprises a second substrate on which second terminal electrodes are formed to be electrically connected to the plurality of first terminal electrodes, a plurality of third terminal electrodes and wires for electrically connecting the second terminal electrodes with the third terminal electrodes are formed on the second substrate, the wires have a function of making conversion from a pitch of the second terminal electrodes to a pitch of the third terminal electrodes, and grooves are formed between the second terminal electrodes respectively.
(17) An ink jet printer in another mode of the present invention comprises an ink jet head having a first substrate on which a piezoelectric element and a plurality of first terminal electrodes are formed, and is characterized in that the ink jet head further comprises a second substrate on which second terminal electrodes are formed to be electrically connected to the plurality of first terminal electrodes, a plurality of third terminal electrodes and wires for electrically connecting the second terminal electrodes with the third terminal electrodes are formed on the second substrate, the wires have a function of making conversion from a pitch of the second terminal electrodes to a pitch of the third terminal electrodes, and grooves are formed between the above described second terminal electrodes respectively.
(18) An ink jet printer in another mode of the present invention comprises an ink jet head having an electrostatic oscillator and a first substrate on which a plurality of first terminal electrodes are formed, and is characterized in that the ink jet head further comprises a second substrate on which second terminal electrodes are formed to be electrically connected to the plurality of first terminal electrodes, a plurality of third terminal electrodes and wires for electrically connecting the second terminal electrodes with the third terminal electrodes are formed on the second substrate, the wires have a function of making conversion from a pitch of the second terminal electrodes to a pitch of the third terminal electrodes, and grooves are formed between the second terminal electrodes respectively.
By forming the grooves between the second terminal electrodes on the second substrate, each of inventions set forth in (14) through (18) described above makes it possible to prevent the terminal electrodes from being deformed by heat and pressure or shorted by outflow of an alloy or a metal at a step of an alloy bonding or a metal bonding even if the electrodes have a narrow pitch. Furthermore, the invention makes it possible to lengthen a creeping distance between adjacent terminal electrodes, thereby suppressing an influence due to noise.
As a result, the invention allows the terminal electrodes to be configured compact on the first substrate, thereby making it possible to manufacture the large number of first substrates from a single semiconductor wafer and enhance productivity, for example, when the first substrate is manufactured from a single semiconductor wafer.
(19) A liquid crystal device in another mode of the present invention comprises a liquid crystal sandwiched between a first substrate and a second substrate, a plurality of first terminal electrodes which are formed on either of the first substrate and the second substrate, and is characterized in that the liquid crystal device further comprises a third substrate on which second terminal electrodes are formed to be electrically connected to the first terminal electrodes, a plurality of third terminal electrodes and wires for electrically connecting the second terminal electrodes with the third terminal electrodes are formed on the third substrate, the wires have a function of making conversion from a pitch of the second terminal electrodes to a pitch of the above described third terminal electrodes, and grooves are formed between the above described second terminal electrodes respectively.
(20) An electronic appliance in another mode of the present invention comprises a liquid crystal device, and is characterized in that the liquid crystal device comprises a first substrate, a second substrate, a liquid crystal sandwiched between the first substrate and the second substrate, and a plurality of first terminal electrodes formed on either of the first substrate and the second substrate, the liquid crystal device further comprises a third substrate on which second terminal electrodes are formed to be electrically connected to the plurality of first terminal electrodes, a plurality of third terminal electrodes and wires for electrically connecting the second terminal electrodes with the third terminal electrodes are formed on the third substrate, the wires have a function of making conversion from a pitch of the second terminal electrodes to a pitch of the third terminal electrodes, and grooves are formed between the second terminal electrodes respectively.
By forming the grooves between the second terminal electrodes on the third substrate, an invention set forth in (19) or (20) described above makes it possible to prevent the terminal electrodes from being deformed by heat and pressure or shorted by outflow of an alloy or a metal at a step of an alloy bonding or a metal bonding even if the electrodes have a narrow pitch. Furthermore, the invention makes it possible to lengthen a creeping distance between adjacent terminal electrodes, thereby suppressing an influence due to noise.
As a result, an area to be occupied by a terminal electrode section of the first substrate or the second substrate can be minimized. Therefore, a large display section can be reserved even if the substrate has an area equal to that of a conventional substrate. Furthermore, the terminal electrodes can be connected with a narrow pitch, so that the number of terminals in a connecting section can be increased. Accordingly, pitches of wires and pixels can be narrow and highly minute.